Piston arrangement for radial engines



P 1941- w. B. GOODMAN 2,255,214

PISTON ARRANGEMENT FOR RADIAL ENGINES Filed Dec. 9, 1939 INVENTOR MLLARD 8.6000m1v ATTORNEY Patented Sept. 9, 1941 PISTON ARRANGEMENT FOR RADIAL ENGINES Willard B. Goodman, Radburn, N. J., assignor to Wright Aeronautical Corporation, a corporation of New York Application December 9, 1939, Serial No. 308,456

Claims.

This invention relates to engines and is particularly concerned with a piston and cylinder arrangement of such character that engine height may be reduced. The invention is adapted for use with radial cylinder engines in which case the engine diameter may be cut down, and

is also adapted for use with V type of engines wherein the distance from the crankshaft center to the cylinder ends may be reduced without materially altering other characteristics of the engine.

The invention contemplates the overlapping of the paths of pistons which are connected to the same crankpin so that in effect, the piston head at bottom center and top center positions may be held closer to the crankshaft center than if the piston paths do not overlap as in conventional practice.

Objects of the invention will be apparent from the above and also from the appended specification and claims, in connection with the drawing, in which:

Fig. 1 is a cross section of a portion of a radial cylinder engine showing the cylinder and the piston relationship;

Fig. 2 is a bottom view of the pistons taken on the line 22 of Fig. 1; and

Fig. 3 is a bottom view similar to Fig. 2 showing an alternative arrangement of the invention.

In Fig. 1 a portion of an engine crankcase is indicated at H], having decks ll formed thereon to which are secured the flanges l2 of cylinders 13 which have portions l4 projecting within the crankcase. The cylinders are in angled relationship, as shown, the relationship illustrated being appropriate for a nine-cylinder radial engine in which the included angle between center lines of adjacent cylinders is 40. It will be noted that the cylinder projections l4 virtually touch one another and in normal practice pistons reciprocating within the cylinder may not pass below the lower ends of these cylinder projections. To provide necessary piston length for any chosen stroke, the cylinders must project outwardly beyond the crankcase a distance which is controlled largely by the radius (from the shaft center) of the inner end of the cylinder extensions.

Now, if it be possible to have the pistons, such as l5, protrude inwardly from the cylinder extensions the height of the cylinders may be reduced in like amount but obviously, unless appropriate provision be made, the pistons would interfere with one another at bottom center position. The invention provides for such overlapping of the pistons at the bottom of their strokes by means shown in Figs. 2 and 3. The bottoms of the piston skirts, near the center plane of rotation, are slotted as at l6, H and as at l8, 19, the slots defining therebetween projections or lands 2!) which may pass within the slots l6, l1, [8, or [9 of the adjacent piston. To provide the necessary rigidity of the piston skirt, the latter may be initially formed with an inward protuberance 22 to accommodate the-slots or notches. In the showing of Fig. 2, each piston would have a right hand and a left hand side so that as shown, to properly assemble the plurality of pistons in a radial cylinder engine, all of the notches l6 and I! would be disposed to the left, or counterclockwise, while all of the notches l3 and I9 would be disposed to the right, or clockwise.

As an alternative arrangement, the lands and grooves may be so arranged that each piston may be assembled without respect to orientation, such an arrangement being shown in Fig. 3. Therein, the central plane of rotation is designated by the center line 30 which defines one side face of a land 3| which, on one side of the piston, lies below the line 30 and on the other side lies above the line 30. Subsequent lands 32 and 33 are defined on either side of the line 30 by intervening slots and accordingly the lands of each piston engage the slots of an adjacent piston regardless of the orientation of either piston.

In applying the invention, it will be noted that a material portion of each piston skirt does not bear upon the cylinder when the piston is close to bottom center position. This, however, is of no great importance for in bottom center position, as in top center position, there is no angularity to the normal connecting rod whereby side thrust of the piston on the cylinder wall is negligible. At such time as rod angularity and side thrust become appreciable, the piston will have traveled upwardly to be fully embraced by the cylinder and the outer surfaces of the above described lands on the bottom of each piston will bear upon the cylinder wall to assume'side thrust and to prevent undue tilting of the piston within the cylinder.

The width of the lands and grooves in the piston skirt is largely a matter of choice depending upon strength of the material used and the area of the land surface contactable with the cylinder wall to assure adequate lubrication. The depth and height of the lands and grooves will obviously be governed by the amount of piston overlap and angle between adjacent cylinders. For greater stability of the pistons at bottom center position, the cylinder projections l4 could be extended inwardly as indicated by the dotted line 35 so that all portions of the pistons are embraced, with the exception of the lands and grooves interlocked with an adjacent piston.

While I have described my invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. In an engine having adjacent cylinders angularly disposed with the adjacent cylinder ends in close proximity, pistons in respective cylinders having their lower skirt ends arranged to protrude from the cylinder ends in certain periods during operation, and: means to prevent interference of the pistons with one another com prising interlocking lands and grooves thereon, said landsbearing on the cylinder walls when the piston is raised in thecylinder to provide in efiect full piston length engagement with the cylinder to attain minimum piston tipping.

2. In an engine having relatively angled cylinders, pistons therein having full length skirts adapted to extend inwardly beyond the inner cylinder ends to an extent that the piston skirts would normally interfere with one-another, said skirts having interengaging lands and grooves to allow of piston overlap without sacrificing normal skirt length.

3. A pair of reciprocable pistons adapted to overlap during part of their travel each piston having a plurality of grooves in the overlapping portions defining tongues between the grooves, the tongues on one piston engaging between the grooves of the other whereby the tongues provide full length piston bearing when the pistons are raised.

4. A piston comprising a head, a skirt and opposed pin bosses within the skirt, and having a plurality of slanted slots at the skirt lower edge parallel to and symmetrically disposed relative to a diametral plane normal to the pin axis, said slots defining intervening lands engageable within the slots of an adjacent similar piston.

5. A piston comprising a head and a depending skirt the latter having slots in its lower edge defining intervening lands which lie parallel to a diametral plane through the piston said slots being formed in diametrically opposite portions of the skirt and being similarly arranged with respect to said diametral plane so that said slots and lands have identical disposition when the piston is turned one-half turn about its axis.

WILLARD B. GOODMAN. 

